A prior-art gasoline engine internal-combustion has as shown in FIG. 1 a manifold tube 2 that connects the high-pressure fuel pump to the fuel injectors of the engine's cylinders. This manifold tube 2 is pressurized normally at about 200 bar and the pressure in it can peak at 450 bar, reaching a staggering 1600 bar for some diesel systems. The tube 2 is typically made of stainless steel so that it can resist both this enormous pressure and the chemical attack of the fuel. As a result of the cost of the steel, its weight, and the difficulty working it, it is invariably made of relatively thin stock so that it is impossible, for instance, to thread ports 5 in it from which the fuel exits to the injectors.
Hence the tube 2 is provided as described in German 100 20 605 and 197 44 762 with saddle fittings 3 that are secured to the outside surface of the tube 2 at the ports 5. Each fitting 3 is formed with a throughgoing passage 4 of a flow cross section that is normally somewhat greater than that of the respective port 5, both normally being circular in section, so that if the passage 4 does not extend perfectly radially of the tube 2 or is not perfectly centered on the respective port 5 the fuel can still pass.
Making up such a manifold assembly 1 is fairly difficult. Once the manifold tube 2 is drilled to have the necessary ports 5, the saddle fittings 3 must be positioned to align their passages 4 perfectly with the respective ports 5, then they are soldered or welded in place at the joint 6. Unfortunately, each saddle fitting 3 covers its port 5 and, since the passage 4 in the fitting 3 is often oriented nonradially of the tube 2, it is impossible to verify the position. Inserting an alignment pin through the fitting passage 4 into the port 5 to ensure proper alignment is moderately effective although difficult to do in a mass-production operation. Typically the fitting 3 is spot-welded to the tube 2 when aligned with a pin, then the entire manifold assembly 1 is welded in one operation, in which case the previously made spot weld blocks the ability of the solder wash to enter the joints 6 between the fittings 3 and the tube 2.
Any misalignment, even a very minor one, creates a restriction that produces turbulence in the passing fluid. When the fitting passage 4 is of greater diameter than the port 5, which is common, the port edges create turbulence even with perfect alignment. What is more, the solder holding the fitting 3 to the tube 2 is exposed to the fuel passing through the assembly and can be attacked by it, weakening the joint and possibly creating a dangerous leak.